1. Field of the Invention
The present invention relates generally to location systems, and more specifically to a location system for a LCS (LoCation Service) client terminal which provides location-based service to a target mobile terminal when the client terminal knows the location of the mobile terminal.
2. Description of the Related Art
In the location system standardized by 3GPP (3rd Generation Partnership Project) TS (Technical Specification Group Services and System Aspects) 23.271 V5.3.0 and 25.305 V5.4.0, LCS clients provide a location-based service to a mobile terminal by using ASP (application service provider) software, only if the mobile terminal is located within the coverage area of the service. Examples of such location-based service are described in 3GPP TS 22.071 V5.1.1 (2002-3). If the location of the mobile terminal is outside of the service coverage area, the LCS client terminal is not required to provide its service to that mobile terminal. However, the client terminal has no way of knowing the location of the mobile terminal, it transmits a location request message to the location system to determine if the mobile terminal is located within the coverage area of its service before initiating a location-based service to the target mobile terminal. In the location system, the location request message from the client terminal is received and processed through a gateway, or GMLC (Gateway Mobile Location Center) and a serving node, or MSC/SGSN (Mobile Switching Center/Serving GPRS Support Node) collaborates with the associated wireless network to perform a location measurement on the target mobile terminal to produce a location estimate and returns a location report message. The location report message is transmitted back to the client terminal through the gateway. Therefore, if a target mobile terminal is roaming outside of the service coverage area of a client terminal, the client terminal decides that no location-based service is necessary on receiving a location report from the associated gateway. As a result, the mobile communication networks consume their resource for useless location request/report traffic when a target mobile terminal is roaming outside of the coverage of location-based service provided by a client terminal. In particular, when the target mobile terminal has moved from its subscribed home network to a foreign network operated by a different network operator, a substantial amount of resources is used in these networks for useless traffic.
It is known that when a client terminal specifies a QoS (quality-of-service) parameter, the associated gateway uses the specified parameter as a threshold for making a decision as to whether a location request message is to be forwarded to the serving node of a target mobile terminal. If the specified QoS parameter is satisfied, the gateway forwards the message to the serving node of the target mobile terminal. Otherwise, an error message is returned to the client terminal. However, the known location system returns no error message to the client terminal when the target mobile terminal is roaming outside of the coverage area of the location-based service provided by the client terminal.